feat: implement Blazor web interface for GM session management

- Created GmRelay.Web project (Blazor Server)
- Created GmRelay.Shared library for domain models and rendering
- Refactored GmRelay.Bot to use the Shared library
- Integrated Telegram Login widget with server-side HMAC verification
- Added Dashboard, Group Details, and Edit Session pages
- Enabled bot notifications and in-place message updates from web actions
- Updated .NET Aspire orchestration and Docker Compose configuration

src/GmRelay.Web/Components/Pages/GroupDetails.razor

@@ -0,0 +1,80 @@
+@page "/group/{GroupId:guid}"
+@using GmRelay.Web.Services
+@using GmRelay.Shared.Domain
+@using Microsoft.AspNetCore.Authorization
+@attribute [Authorize]
+@inject SessionService SessionService
+
+<PageTitle>Group Sessions - GM-Relay</PageTitle>
+
+<div class="container mt-4">
+    <nav aria-label="breadcrumb">
+      <ol class="breadcrumb">
+        <li class="breadcrumb-item"><a href="/">Dashboard</a></li>
+        <li class="breadcrumb-item active">Group Sessions</li>
+      </ol>
+    </nav>
+
+    <h2>Upcoming Sessions</h2>
+
+    <div class="mt-4">
+        @if (sessions == null)
+        {
+            <p>Loading sessions...</p>
+        }
+        else if (sessions.Count == 0)
+        {
+            <div class="alert alert-info">No upcoming sessions found for this group.</div>
+        }
+        else
+        {
+            <div class="table-responsive">
+                <table class="table table-hover align-middle">
+                    <thead class="table-light">
+                        <tr>
+                            <th>Title</th>
+                            <th>Time (MSK)</th>
+                            <th>Status</th>
+                            <th>Link</th>
+                            <th>Action</th>
+                        </tr>
+                    </thead>
+                    <tbody>
+                        @foreach (var session in sessions)
+                        {
+                            <tr>
+                                <td>@session.Title</td>
+                                <td>@session.ScheduledAt.FormatMoscow()</td>
+                                <td>
+                                    <span class="badge @GetStatusClass(session.Status)">@session.Status</span>
+                                </td>
+                                <td><a href="@session.JoinLink" target="_blank" class="text-truncate d-inline-block" style="max-width: 150px;">Link</a></td>
+                                <td>
+                                    <a href="/session/edit/@session.Id" class="btn btn-sm btn-outline-secondary">Edit</a>
+                                </td>
+                            </tr>
+                        }
+                    </tbody>
+                </table>
+            </div>
+        }
+    </div>
+</div>
+
+@code {
+    [Parameter] public Guid GroupId { get; set; }
+    private List<WebSession>? sessions;
+
+    protected override async Task OnInitializedAsync()
+    {
+        sessions = await SessionService.GetUpcomingSessionsAsync(GroupId);
+    }
+
+    private string GetStatusClass(string status) => status switch
+    {
+        SessionStatus.Confirmed => "bg-success",
+        SessionStatus.Cancelled => "bg-danger",
+        SessionStatus.ConfirmationSent => "bg-warning text-dark",
+        _ => "bg-secondary"
+    };
+}